Semiconductor devices may be based on different semiconductor materials, for example, silicon, gallium-arsenide and group III-nitrides. A group III-nitride-based semiconductor device, in which gallium nitride is used as part of the semiconductor materials, has a larger bandgap and a higher critical field compared to the semiconductor device which uses silicon as the main material.
By way of example, a group III-nitride-based semiconductor device may include an aluminium gallium nitride/gallium nitride heterostructure field effect transistor or a high electron mobility transistor (HEMT). Such devices may be formed by depositing layers of appropriate composition and thickness epitaxially on a substrate such as a sapphire substrate, a silicon substrate or a silicon carbide substrate.
A group III-nitride-based semiconductor device may provide a semiconductor device having a low on-resistance and low loss. Such semiconductor devices may be useful for power control, for example. Reducing the device output capacitance may be desirable.